View source for Long duration space flight

The number of astronauts who have been in space for a long time is steadily increasing.  The number people who have spent more than a year in space currently (2024) numbers 52. <ref>http://www.spacefacts.de/english/e_tis.htm| Astronauts & Cosmonauts Sorted by Time In Space</ref>

The longest time spent in space is currently 878 days, 11 hours, & 29 minutes, by Gennadi Ivanovich Padalka of the USSR. 


==Cumulative Radiation Exposure==
The radiation received in the International Space Station is 144 milliSievert / year.  This is about 28% of the radiation dose of a 2.5 year Mars mission (assuming a mission where the total radiation exposure is 520 mSv over 2.5 years).  See the Mars Direct Mission, described in the "Case for Mars", by Robert Zubrin.

This number does not mean much, but these values might give some perspective:
* One dental X-Ray is: 0.005 mSv.
* Radiation on a flight from LA to New York: 0.04 mSv.
* the radiation (from [[Cosmic Radiation | cosmic rays]]) in Vancouver B.C (at sea level) is 0.30 mSv / year.
* the radiation (from cosmic rays) from the top of Mt. Lorne, Yukon (at 2,000 m) is 0.84 mSv / year.<ref>https://www.cnsc-ccsn.gc.ca/eng/resources/radiation/radiation-doses/# |Gov of Canada, Radiation Doses</ref>
* The radiation received a typical person on Earth (from all sources) is 6.2 mSv per year.
* One chest medical CT scan is 7 mSv.
* USA one year dose for worker in Nuclear Industry: 50 mSv / year.

* the average radiation in the city Ramsar, Iran is 260 mSv / year.  (The people in this city do not show any health effects from this high dose.  A maximum safe value?)
See: <ref>https://pubmed.ncbi.nlm.nih.gov/11769138/ | Very high background radiation areas of Ramsar, Iran: preliminary biological studies.</ref>, <ref>https://www.ecolo.org/documents/documents_in_english/ramsar-natural-radioactivity/ramsar.html</ref>, 
<ref>https://aerb.gov.in/images/PDF/image/34086353.pdf | Ramsar suggests that current regulations for radiation are too strict.</ref>, <ref>https://www.sciencedirect.com/science/article/abs/pii/S0531513104018369 | Natives of Ramsar had better response to high gamma ray doses</ref>, <ref>https://www.researchgate.net/publication/228757260_Are_the_Inhabitants_of_High_Background_Radiation_Areas_of_Ramsar_More_Radioresistant_Scope_of_the_Problem_and_the_Need_for_Future_Studies</ref>, <ref>https://www.ntanet.net/the-naturally-occurring-high-radiation-levels-of-ramsar-iran/</ref>


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==References:==